1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly to an LCD comprising a biaxial compensation film.
2. Description of the Prior Art
Owing to their low-profile, thin, and lightweight features, LCDs have become the mainstream display devices in recent years. Liquid crystal screens are widely used in electronic devices such as cellphones, personal digital assistants (PDAs), digital cameras, computers, notebooks, etc.
An LCD comprises an LC cell. An alignment of LC molecules in the LC cell is determined by variation of an electric field applied on the LC cell, and the transmission of light in the LC cell is adjusted accordingly. An LC material has a property of birefringence, which means that the refractive index of light in the direction of the long axis of the molecules is different from the refractive index of light in the direction of the short axis of the molecules. Therefore, linearly polarized incident light has diverse phases through different paths in the LC cell in the polarized direction. The feature of color and the transmission of light at a slant viewing angle are different from those at a front viewing angle.
Birefringence index of the LC molecules in the LC cell varies with an observation inclination. With the observation inclination increases, both of the contrast ratio of an image and image resolution decrease. To enhance the contrast ratio of the image obviously at a specific viewing angle and to reduce leakage of light in dark state on the LCD, a compensator film is attached to the LC panel of a conventional LCD. The birefringence of the LC molecules can be symmetrically compensated because the retardation value of light in different directions is compensated using the compensator film.
A bi-layered compensator film has advantages of reducing leakage of light in dark state on the LCD effectively and enhancing the contrast ratio and resolution at a wide viewing angle. However, the bi-layered compensator film is expensive, so production cost cannot be reduced. Contrarily, production cost can be effectively reduced using a unilayered compensator film while an increase in leakage of light in dark state of the LCD seems inevitable.